1. The Field of the Invention
The present invention relates to flange unions of the type adapted to join two conduits for fluids and thereby form a conduit joint therebetween. The invention is further concerned with conduit joints including the flange union described and claimed herein, and piping systems comprising one or more of the said flange unions and/or joints.
2. The Prior Art
Flange unions have been used extensively heretofore to detachably join the ends of two conduits and thereby form a continuous length with a separable fluid tight seal or joint therebetween. The resultant structure provides for permanency of the installation when desired and also allows future changes and modifications to be made easily and without demaging or destroying the flange unions, the attached conduits, and/or other cooperating apparatus attached thereto. However, the prior art flange unions have a number of disadvantages and deficiencies which prevent them from being entirely satisfactory in all respects.
For example, one prior art flange union for joining conduits employs a gasket between the opposed terminal inner ends of a pair of flange members and a sealing pressure is applied thereto by means of a plurality of circumferentially spaced bolts. This flange union structure has a large annular sealing area which extends from the internal diameter of the bore outward to the bolts. The total force or pressure that must be exerted on a psi basis by tightening the flange bolts is very great due in part to the large surface area of the seal. Also, the average length of the moment arm that exists between the bolts and the points at which the sealing pressure is applied over the large sealing area is short and the mechanical advantage of the bolts is low. Inasmuch as the flange bolts are under constant stress due, among other reasons, to pressure surges in the conduits, vibration and outside forces applied to the conduits, they wear excessively fast and tend to develop stress cracks which ultimately cause mechanical failure. As a result, it is necessary to replace the bolts in prior art flange unions at frequent intervals. This is a time consuming and costly procedure which has the further disadvantage of lost production as the equipment must be taken off stream during the repairs.
The prior art flange unions described above are not self-aligning and thus are difficult to align properly under the installation conditions which exist on many jobs. They also have the disadvantage of not sealing properly when the flange members are mis-aligned initially, or when the flange members are knocked out of alignment during use. The above prior art flanges are not fire resistant and fail quickly in the event of a fire, they do not have a back-up secondary and/or tertiary seal which may be relied upon in the event of failure of the primary seal, and provision is made for replacable inserts or other means to increase the life of the seal surfaces.
The aforementioned deficiencies and disadvantages of the prior art flange unions have been long recognized by those skilled in this art. However, an entirely satisfactory alternative thereto was not available prior to the present invention in spite of the long existing and great need therefor.